Can cell cultures from fish be used to study obesity in humans?

Studies of overweight carp show that they react similar to humans when they are given medication for obesity and high cholesterol. The question now being posed by scientists is whether studies of fish cells can shed light on the causes of an unbalanced fat metabolism in humans.

Fish, rats and humans have more in common than might be imagined. Due to similarities in fundamental metabolic processes, fish cells might serve as a tool to provide more information about human obesity.

In a study, young grass carp, which are basically herbivorous, were fed a high fat diet for six weeks. This diet is unnatural for the carp, and the fish became very obese. Further, the carp were given a feed containing the medication fenofibrate for two weeks. Fenofibrate is normally used to lower the cholesterol level and reduce the formation of triacylglyserol (a constituent of fat) in humans.

"The obese carp had a high content of triacylglyserol in the blood, which is a known marker in the blood of obese persons or persons with type II diabetes. The cholesterol level was also high. When fenofibrate was given, the fat metabolism of the carp increased while the content of both triacylglyserol and cholesterol in the blood decreased," says Livar Frøyland, head of research on the Seafood and Health Research Programme at the National Institute of Nutrition and Seafood Research (NIFES) in Norway. The study was carried out at Sun Yan-sen University in China.

"The carp's response showed a high level of correspondence with the metabolic reactions observed in obese persons and rats which have been fattened up and then given fenofibrate. Concurring reactions among these three different species indicate that universal and very fundamental mechanisms control the fat metabolism processes.

"Basic metabolic processes can be studied using cells. Further studies will focus on fat combustion and fat synthesis in cells from fish, rat and humans in order to understand the underlying causes of the metabolic disturbances we see in humans struggling with obesity and type II diabetes," says Frøyland.

Indicators of lifestyle-related diseases

Triacylglyserol is a constituent of fat which plays an important role in the body's metabolism, both as a source of energy and as a transporter of fat in the human body. The triacylglyserol content in the blood gives an indication of the amount of fat that has been consumed or the amount of fat the liver produces and passes into the blood.

"An elevated content of triacylglyserol in the blood is one of many indicators of lifestyle-related diseases, such as obesity," says Frøyland.

"Correspondingly, an elevated content of the "unhealthy" LDL cholesterol is a known risk factor for cardiovascular diseases. Eating fish with a high fat content increases the proportion of the"healthy" HDL cholesterol in the blood and reduces the level of the "unhealthy" LDL cholesterol. A recent study carried out among men in China showed that those who ate farmed fish five times a week experienced a 20% reduction in disease markers for cardiovascular diseases, as well as a healthier blood fat profile".